It is well known in the art to utilize a heat stake in order to fasten a plastic part in position.
As illustrated in FIGS. 1 and 2, a typical heat stake S includes a tapered cylindrical sidewall W having a hollow core C. More specifically, the taper is toward the distal end D of the heat stake S and results from a design draft to allow the plastic part P to be removed from an injection molding tool. As a result, the wall W of the heat stake S includes a greater cross-sectional area and perimeter at the proximal end E adjacent the plastic part P than at the distal end D. The increased cross-sectional area of the heat stake S at the proximal end E where the heat stake S is joined with the plastic part P has a tendency to promote sink marks in the surface A of the plastic part P. This increases material usage, product waste and cost.
This document relates to a new and improved heat stake for a plastic part that effectively reduces the cross-sectional area of the heat stake at the proximal end where the heat stake is joined with the plastic part thereby avoiding sink marks in the A surface of the plastic part even when the plastic part includes relatively thin cross sections. Advantageously, this is achieved without adding tooling actions in the injection mold tools to form the associated undercut features.